If you are not worried about taking the water out away from the building and just want to be able to run out of the door without going thru a waterfall. There are diverters that go on top of the roofing and are part of that system and have to be built into the roofing system. They are not visible.

If you want simple and effective I have put up just a short section of gutter with both ends open a few feet longer than the door width. Great for garage or barn doors and with the open ends no need for cleaning. If the looks are ok and you don’t have an issue with water coming down on both sides of the door it works the same as a diverter and much simpler.

A diverter can be added, but it has been my experience that they can and usually do create problems. The problem is water wants to flow downhill in a positive manner and when a diverter is added you are sending water across the path it wants to flow.

Diverters trap debris, leaves, shingle granules and are usually forgotten and not maintained. A water dam is created and hydraulic water action can develop, sending water up and under your roof system. A gutter under the roof edge, would be a better solution if possible.